The proposed research aims to evaluate the role of Ca2 ion binding proteins and their role in mediating the control by Ca2 ion of intracellular enzymes in nerve cells and in human erythrocytes. The Ca2 ion binding protein which serves as the receptor for Ca2 ion in erythrocytes stimulates the Ca2 ion transport ATPase. The erythrocyte protein is biologically cross-reactive with the Ca2 ion binding protein from brain which stimulates the cyclic nucleotide phosphodiesterase from brain. It is proposed to investigate the possibility that the Ca2 ion binding protein from brain activates the Ca2 ion transport ATPase in brain and to demonstrate its activation of the associated pumping of Ca2 ion out of the brain cell. It is also proposed to investigate the possibility that the Ca2 ion binding protein serves as the receptor which initiates exocytosis of neurotransmitters. The second aspects of the proposal is to develop the assay for the presence of Ca2 ion binding proteins, based on their activation of the Ca2 ion transport ATPase of erythrocytes, so that it can be used in a clinical setting for the determination of the level of this protein. The high resemblance between this protein and the Ca2 ion binding protein from brain suggest that its presence may be related to crucial neurological processes. In order to determine the degree to which the erythrocyte and nervous system proteins resemble one another, comparative physical and chemical studies will be performed on the two proteins; these studies will compare the amino acid composition, spectroscopic, hydrodynamic, fluorescent electrophoretic and ion binding properties of the two proteins. This determination of the relationship between the brain and erythrocyte proteins should help in evaluating the value of the proposed clinical assay.